How to overlay someone (and his/her movements) in a video clip tracking eyes,face,mouth of a 3d character
Well, first of all I would be surprised if this would work at all.
The faces you are tracking are so extremely tiny, that the solver has barely a chance to solve that correctly.
Second, you have a moving camera, so you should solve that first.   

So first track the room and solve the camera for that.
Then, in the objects panel of the clip editor's sidebar, add an object and then place markers on the person's head and try to solve it. 
But as I said, I really don't think it's possible, considering how tiny the persons are in relation to the frame size and how blurry the footage is.